This invention relates generally to the field of antennas. More specifically, this invention relates to an ultra-broadband antenna that is incorporated into a garment that may be worn around a human torso and uses radiation absorber material to mitigate radiation hazards.
Soldiers today have a need to communicate many different types of information that may include global positioning information, voice signals, video, and technical data. Most antennas of hand-held radios used by soldiers for tactical operations are monopoles or dipoles that extend from a radio carried by the soldier. Such antennas have many disadvantages. For example, monopole antennas are narrowband and provide efficient operation over only a small frequency range. However, broadband antennas are needed to accommodate frequency-hopping systems that resist jamming. Some commercial antennas are excellent for several frequency bands but are useless at any other frequency. For frequency-hopping systems, efficiency is required in a wide band of contiguous frequencies. Thus, it may be appreciated that collectively, a soldier needs to have wideband communication capabilities. Monopole antennas do not provide such broadband operating capability. Also, monopole antennas are clumsy and tend to snag on trees, brush and low ceilings. Most importantly, the monopole antennas provide a visible signature that distinguishes the radio operator and any accompanying officer nearby, making them vulnerable to sniper fire. Because disruption of command, communications, and control is a paramount goal of snipers, reduction of the visual signature of an antenna is highly desirable. Therefore, a need exists for a broadband, man-carried antenna that does not have a readily identifiable visual signature.
In addition to the need for a broadband, man-carried antenna that does not have a readily identifiable visual signature, a primary requirement for any antenna is safety. This safety pertains to radiation hazards to persons, ordnance, and fuel. A person""s maximum exposure to electromagnetic fields, as defined by standards adopted by the Department of Defense, the Department of the Navy, and the Institute of Electrical and Electronics Engineers (IEEE), depends upon the frequency, volume of body exposed, and length of time of exposure. Thus, it may be appreciated that an antenna incorporated into a garment must be safe for any input power and frequency with which it will be used since the antenna will be in close proximity to, at least, the radio operator. Therefore, a need exists for a broadband, man-carried antenna that does not have a readily identifiable visual signature and that maintains acceptable RF energy absorption levels.
The invention is directed to an ultra-broadband antenna that is incorporated into an electrically nonconductive garment and includes radiation absorber material to mitigate radiation hazards. The antenna operates over a frequency range of about 35-500 MHz.
The antenna is integrated into a garment so that the antenna offers no distinctive visual signature that would identify the person wearing the antenna garment as a radio operator. The garment is made of an electrically nonconductive material. The antenna includes first and second radio frequency (RF) elements attached to the garment so that a gap exists between them, where the RF elements each form a band when the garment is worn by a wearer. RF and ground feeds are electrically connected to the first and second RF elements, respectively. A shorting strap electrically connected between the first and second RF elements on the anterior side of the garment generally opposite the feed helps match the antenna impedance to an external device, such as a signal generator. The gap provides a voltage difference between the RF elements when the antenna is energized. Electrically conductive straps that extend over the shoulder regions of the garment are electrically connected between the anterior and dorsal regions of the first RF element. An impedance matching circuit electrically connected between the first RF element and the RF feed may be employed to approximately match the impedance of the antenna with an external device and the wearer to optimize the efficiency of the antenna for a particular operating band.
To mitigate radiation hazards posed by the antenna to the human wearer, radiation absorber material is disposed along the length and width of the gap between the RF elements. In addition, radiation absorber material is disposed in a pocket sewn on the inside layer of the antenna garment in the region of the RF feed.
These and other advantages of the invention will become more apparent upon review of the accompanying drawings and specification, including the claims.